Zeolite Beta is one of a number of synthetic crystalline zeolites discovered in recent years which, in the as-synthesized state, can have a silica to alumina ratio greater than 10. The synthesis and characteristics, including its X-ray diffraction pattern, are described in U.S. Pat. No. Re.28,341 to Wadlinger et al. The entire contents of U.S. Pat. No. Re.28,341 are incorporated herein by reference as if fully set forth. The use of Zeolite Beta for the hydroconversion of hydrocarbons has been described in several patents. For example, U.S. Pat. No. 3,923,641 to Morrison describes and claims the hydrocracking of C.sub.5 + naphthas with high selectivity for isobutane. U.S. Pat. No. 4,428,819 to Shu discloses a process for hydrofinishing a hydrodewaxed oil over Zeolite Beta. U.S. Pat. No. 4,419,220 to La Pierre et al. discloses and claims a process for dewaxing a feedstock containing straight chain paraffins over Zeolite Beta. All of these processes utilize a catalyst that contains a hydrogenation component.
Among the hydroconversion processes, catalytic hydrocracking is a petroleum refining process of increasing importance due to the similarly rapid increase in the demand for middle-distillate fuels. In general the process comprises converting heavy petroleum feedstocks, a substantial fraction or all of which boils above about 700.degree. F. at atmospheric pressure, to lower-boiling products in the range of about 300.degree. F. to about 700.degree. F., e.g. to gasoline, petrochemical naphthas, furnace oil, and diesel and turbine fuels. The catalysts employed are of the dual functional type and comprise a hydrogenation-dehydrogenation component, such as a Group VIII noble metal, or a combination of Group VIII and Group VIA metal, in combination with a solid acid support, such as silica-alumina or an aluminosilicate, which is the acidic cracking component.
Of the solid acid components, it is generally considered that zeolitic aluminosilicates are the most active in the sense that they convert the highest fraction of feedstock to products under reasonable operating conditions. However, activity is only one requirement. Equally important is stability, which is a measure of the useful operating life of the catalyst. To achieve reasonable catalyst stability in a hydrocracking operation, it has been heretofore necessary to operate at relatively high hydrogen pressures, e.g. at pressures from about 1500 to as high as 4000 pounds per square inch.
It is an object of this invention to provide a novel hydrocracking catalyst composition of improved stability. It is a further object of this invention to provide an improved hydrocracking process for converting hydrocarbon feeds. It is a further object to provide an improved hydrocracking process for converting heavy petroleum feedstocks to lower boiling products in the range of C.sub.5 + to about 700.degree. F. It is a further object of this invention to provide a process for hydrocracking heavy petroleum feedstocks at a pressure not greater than about 1000 psig. These and other objects will become apparent to one skilled in the art on reading this entire specification including the appended claims.